Continuous microfilmer timing circuit

ABSTRACT

For use in a continuous microfilmer, a timing circuit includes an SCR gate effective when turned on and off for respectively energizing and de-energizing shutter and clutch coils of such microfilmer. The timing circuit further includes a switch which, when engaged by the lead edge of a document to be microfilmed, causes a first charging circuit, after a predetermined time delay, to turn on the SCR thereby energizing the coils. When the switch disengages from the document a second charging circuit is energized which, after another predetermined time delay, causes the SCR to turn off thereby de-energizing the shutter and clutch coils.

Mn b mm a M m United States Patent Howard CONTINUOUS MICROFILMER TIMING CIRCUIT Inventor:

Primary Examiner-Samuel S. Matthews Assistant Examiner--Michael D. Harris Dwight T. Howard, Rochester, NY.

Attorney-W. H. J. Kline and R. L. Owens [73] Assignee: Eastman Kodak Company,

[57] ABSTRACT For use in a continuous microfilmer, a timing circuit includes an SCR gate effective when turned on and off for respectively energizing and de-energizing shutter Rochester, NY.

May 24, 1971 221 Filed:

Appl. No; 146,232

and clutch coils of such microfilmer. The timing circuit further includes a switch which, when engaged by [52] U.S. Cl. ........................355/14, 355/42, 355/64,

the lead edge of a document to be microfilmed, causes a first charging circuit, after a predetermined time delay, to turn on the SCR thereby energizing the coils.

[51] Int. 21/00 .355/64, 14, 42;

[58] Field of Search..........................

When the switch disengages from the document a second charging circuit is energized which, after another predetermined time delay, causes the SCR to turn off thereby de-energizing the shutter and clutch coils.

[56] References Cited UNITED STATES PATENTS 2,403,711 7/1946 Egan 5 Claims, 1 Drawing Figure lllllA HOWAR D INVENTOR.

PATENIEDHAY 8.1575

DWl GHT T I BY M 6 o E o. 8. z. $536 I656 CONTINUOUS MICROFILMER TIMING CIRCUIT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to timing circuits, and more particularly, to timing circuits for controlling the actuation of shutter and clutch coils of the photographic unit of a continuous microfilmer.

2. Description of the Prior Art In continuous microfilmers, a switch member is often provided which is engaged by the document to be photographed and moved to a position where it actuates a circuit which energizes shutter and clutch coils of the photographic unit of the microfilmer. Since it is desirable that the switch should be spaced from the document image field, the circuit which energizes the shutter and clutch coils introduces a time delay so that the shutter and clutch coils are energized just as the leading edge of the document reaches the exposure station aperture. After the trailing edge of the document clears the exposure aperture, means are provided to deenergize the shutter and clutch coils. An example of such a circuit is disclosed in commonly assigned U.S. Pat. No. 2,403,711 in the name of J. F. Egan.

While the delay circuits previously employed have generally operated in a satisfactory manner, they have been subject to disadvantages such as a lack of timing accuracy.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a timing circuit for a continuous microfilmer which is accurate, readily adjustable over wide time intervals with a higher reliability and is simple to manufacture.

Another object of this invention is to provide a timing circuit which is especially suitable for energizing and de-energizing shutter and clutch control coils of the photographic unit of a continuous microfilmer.

A still further object of this invention is to provide a timing circuit which is relatively insensitive to temperature variations.

In the disclosed embodiment of the invention there is provided a timing circuit which includes an SCR coupled between the clutch and shutter coils of a microfilmer and a source of potential. The timing circuit further includes a switch member which is movable to a first position for coupling a first charging circuit to the potential source. The first charging circuit, after first adjustable time interval, sufficient to permit the leading edge of the document to reach the exposure station aperture, produces a gating pulse to the SCR which is effective to cause the SCR to conduct and apply the potential from the source across the clutch and shutter coils. The switch member is movable to a second position after disengagement with the document wherein it couples a second charging circuit to the potential source. The second charging circuit, after a second adjustable time interval sufficient to permit the trailing edge of the document to clear the exposure station aperture, is effective to drive the SCR into a nonconductive mode thereby de-energizing the clutch and shutter coils.

The invention and its objects and advantages will become more apparent in the detailed description in the detailed embodiment presented below.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description of the preferred embodiment of the invention presented below, reference is made to the sole FIGURE of the accompanying drawing which is a schematic diagram of an exemplary timing circuit 10 in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing there is shown a time delay circuit for use with a continuous microfilmer such as described in part in the above-identified U.S. Pat. No. 2,403,711. The microfilmer includes belts 13 and 14 which carry a document 12 to be photographed to an exposure station, not shown. The belts are driven by a continuously rotating pulley 17 to a position wherein the document engages a document sensing mechanism 15. The mechanism 15 includes a flexible spring finger 18 rotatably mounted about an axle l7 and urged in a counter-clockwise direction by a spring member 22. When the lead edge of the document 12 engages the finger 18, the finger 18 is rotated against the urging of the spring 22 in a clockwise direction. The finger 18 is coupled by a linkage 23 (shown only in dotted line) which moves a switch 11 to a position wherein it disengages from a contact 24 and engages a contact 27. The switch 11 will remain in engagement with the contact 27 as long as the finger 18 is engaged by a document 12. However, as soon as the trail edge of the document disengages from the finger, the spring 22 rotates the finger 18 back to its normal position which causes the switch 11 to disengage from the contact 27 and move into engagement with the contact 24. Although document sensing mechanisms may take various forms known in the art, the mechanism disclosed in commonly assigned U.S. Pat. No. 3,254,167 entitled, SHEET RESPONSIVE CONTROL DEVICE issued May 31, 1966, in the name of C. Altmann is especially suitable for use with the circuit 10.

The timing circuit 10 is coupled to a source of suitable DC potential applied across terminals 41 and 42 and includes a clutch control coil 71 and a shutter control coil 72. As described more fully in the aforementioned U.S. Pat. No. 2,403,71 1, the coil 71 operates the magnetic clutch in the film advancing train and the coil 72 operates an open and closing mechanism for a shutter in the photographic station wherein the document is to be photographed. The coils 71 and 72 are connected in parallel with both connected in series with the positive terminal 41 and the anode electrode of an SCR 58 which has its cathode electrode electrically coupled to the terminal 42. The operation of SCR elements in circuits is well known in the art and is described, for example, in U.S. Pat. No. 3,176,212 issued Mar. 30, 1965 to R. P. DePuy. In the circuit 10, the SCR 58 when in a nonconductive state blocks the flow of current and is thereby effective to cause the coils 71 and 72 to be in a deenergized state. However, when a positive pulse is applied to the gate electrode, the SCR conducts and the coils 71 and 72 will be energized. The SCR 58 will continue conduction until its cathode-anode electrodes are back biased.

Assuming that a document 12 has just moved into engagement with the finger 18, this causes the switch 11 to be moved into engagement with the lower contact 27. A conductive path is now established from the positive terminal 41 through a resistor 47 by way of leads 44 and 43 to a first charging circuit which includes an adjustable resistor 51, a fixed resistor 52 and a charging capacitor 53. After the capacitor 53 develops a predetermined charge level, it will cause a unijunction transistor 54 to fire or conduct which causes a signal to be applied to the gate electrode of the SCR 58 as will be described more fully hereinafter. The time to charge the capacitor 53 to reach the threshold value or firing potential level for the unijunction transistor 54 is referred to herein as the first adjustable time delay interval and is substantially determined by the value of resistance of the elements 52 and 51 in series with the capacitor 53. A shorting adjustment for the variable resistor 51 provides a fine scale adjustment which permits an accurate adjustment of the first time delay interval. The first time delay interval is selected to permit the coils 71 and 72 to be energized just as the leading edge of the document 12 reaches the exposure station aperture, not shown. A blocking path through a diode rectifier 55 and the resistor 56 is connected in parallel across the series combination of the resistors 51 and 52.

The first base electrode of the unijunction transistor 54 is electrically coupled to the resistor 47, and the second base electrode is coupled to the electrical junction of the gate electrode of the SCR 58 and a resistor 57. A zener diode 48 clamps the voltage at the junction of the first base electrode of the transistor 54 and the resistor 48 to a predetermined positive level. When the charge developed across the capacitor 53 reaches the firing potential of the unijunction transistor 54, the transistor 54 becomes conductive and the capacitor 53 discharges through the transistor 54 and the resistor 57. This action produces a positive going signal which is applied to the gate electrode of the SCR 58 and switches it into a high conductive state. The clutch control coil 71 and the shutter control coil 72 are now effectively coupled across the terminals 41 and 42 and are energized permitting them to perform their respective functions in the continuous microfilmer.

When the document 12 disengages from the finger 18, the finger is returned to its normal position and the switch 11 moves into engagement with the contact 24. Just prior to this time, an NPN transistor 73 was in a fully saturated conductive mode caused by the flow of current through resistor 74 and a zener diode rectifier 77. However, when the switch 11 moves into engagement with the contact 24, the potential level at the base electrode of the transistor 73 will swing relatively negative and turn the transistor 73 off. A capacitor 78 embodied in a second charging circuit now begins to charge. The capacitor 78 is charged by the flow of current through variable resistor 81 and fixed resistor 82. After the capacitor 78 develops a predetermined charge level which is equal to the threshold or firing potential level of a unijunction transistor 83, the transistor 83? is switched to a conductive mode and the capacitor 78 starts to discharge through the transistor 83 and a resistor 86. Since the base electrode of a transistor 87 is connected at the electrical junction of the transistor 83 and the resistor 86, a positive signal is applied to the base electrode of the transistor 87 which switches it on. A shunting path is now established across the SCR 58 via the collector-emitter path of the transistor 87 and the SCR 58 switches off. However, the clutch coil 71 and the shutter coil 72 remain energized as a circuit is still completed for these elements through the collector-emitter path of the transistor 87. At this time, a capacitor 102 connected in series with a resistor 101 starts to discharge through the transistor 87. The discharge time of the capacitor is sufficient to insure that the transistor 87 is held in a conductive mode for an interval of time necessary to turn the SCR 58 off. Shortly thereafter, the capacitor 78 will be discharged to a level which causes the transistor 87 to switch off. All possible circuit paths for shutter and clutch are now opened and so they de-energize. The time needed to charge the capacitor 78 to reach the firing voltage of the unijunction transistor 83 when added to the time necessary to switch the transistor 87 on and then off is the time interval needed to de-energize the coils 71 and 72 after the switch 11 has moved into engagement with contact 24 and is referred to in this disclosure as the second adjustable time delay interval. The second time delay interval may be varied by adjusting the shorting adjustment for the variable resistor 81'. The second time delay interval is selected to permit the coils 71 and 72 to remain energized until the trailing edge of the document has passed the exposure station. The series combination of the resistor 101 and the I capacitor 102 prevents the SCR from being switched back to a conductive mode as may result in a rapid and uncontrolled application of a positive signal applied to the anode electrode of the SCR 58.

After the transistor 87 is switched off, current will flow through a resistor 103, a diode rectifier 104 and the zener diode 77 to the base of the NPN transistor 73. A diode rectifier 109 is connected as a series element between a resistor 103 and the collector electrode of the transistor 87. The bias applied to the base of the transistor 73 now switches the transistor 73 into a saturated conductive mode. A circuit is now closed through potentiometer 81, resistors 82 and 107, and the collector electrode of the transistor 73 to the negative terminal 42, which diverts current from the unijunction transistor 83 and prevents the triggering thereof.

Briefly reviewing the operation of the timing circuit 10, when the switch 11 is moved into engagement with the terminal 27, a capacitor 53 begins to charge until a threshold level which causes the unijunction transistor 54 to conduct. The conductive action of the transistor 54 causes a positive signal to be applied to the gate electrode of an SCR 58. The SCR 58 is now driven into conduction and a circuit path is completed from the positive terminal 41 through the clutch coil 71 and the shutter coil 72 to the negative terminal 42. When the finger 18 disengages from the trailing edge of the document 12, the switch 11 is moved into engagement with the terminal 24 which action causes the capacitor 78 to charge. When the capacitor 78 develops a charge sufficient to cause the unijunction transistor 83 to fire, a transistor 87 will be driven into a conductive mode which causes the SCR 58 to be turned off. The circuit 10 is now ready to repeat the operation.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. In a microfilmer including a source of potential, and energizable clutch and shutter coils, and means which continuously moves a document to be photographed, a timing circuit for actuating the clutch and shutter coils as the lead edge of the document moves into a position for photographic exposure and de-energizing the shutter and clutch coils as the trail edge of the document clears the exposure position comprising:

a. gating means connected between the potential source and the clutch and shutter coils and effective in a first condition for preventing the application of the potential of the source across the shutter and clutch coils and effective in a second condition for applying the potential of the source across the shutter and clutch coils;

. first charging means adapted to be coupled to the potential source and for causing said gating means to switch from said first to said second condition a predetermined time delay interval after said charging means is coupled to the potential source;

c. second charging means adapted to be coupled to the potential source and for causing said gating means to switch from said second to said first condition a predetermined time delay interval after said charging means is coupled to the potential source; and

d. switch means engageable by a document to be photographed and movable to a first position in response to engagement by the moving document for coupling the first charging means to the potential source; and movable to a second position upon disengagement with the document for coupling the second charging means to the potential source.

2. The invention as set forth in claim 1 wherein said first charging means includes, a first capacitor for developing a charge, first variable resistance means for adjusting the rate of charge of said first capacitor and first circuit means coupled to said first capacitor and said gating means and responsive to a first predetermined charge level on said first capacitor for switching said gating means from said first to said second condition.

3. The invention as set forth in claim 2 wherein said second charging means includes a second capacitor for developing a charge, second variable resistance means for adjusting the rate of charge of said second capacitor and second circuit means coupled to said second capacitor and said gating means and responsive to a second predetermined charge level on said second capacitor for switching said gating means from said second to said first condition.

4. The invention as set forth in claim 3 wherein said gating means comprises an SCR having cathode and anode electrodes respectively connected in series with the potential source and the device, and a gate electrode coupled to the first circuit means, and wherein in said first condition said SCR is nonconductive and in said second condition said SCR conducts.

5. The invention as set forth in claim 4 wherein said first and second circuit means each respectively include a unijunction transistor. 

1. In a microfilmer including a source of potential, and energizable clutch and shutter coils, and means which continuously moves a document to be photographed, a timing circuit for actuating the clutch and shutter coils as the lead edge of the document moves into a position for photographic exposure and de-energizing the shutter and clutch coils as the trail edge of the document clears the exposure position comprising: a. gating means connected between the potential source and the clutch and shutter coils and effective in a first condition for preventing the application of the potential of the source across the shutter and clutch coils and effective in a second condition for applying the potential of the source across the shutter and clutch coils; b. first charging means adapted to be coupled to the potential source and for causing said gating means to switch from said first to said second condition a predetermined time delay interval after said charging means is coupled to the potential source; c. second charging means adapted to be coupled to the potential source and for causing said gating means to switch from said second to said first condition a predetermined time delay interval after said charging means is coupled to the potential source; and d. switch means engageable by a documenT to be photographed and movable to a first position in response to engagement by the moving document for coupling the first charging means to the potential source; and movable to a second position upon disengagement with the document for coupling the second charging means to the potential source.
 2. The invention as set forth in claim 1 wherein said first charging means includes, a first capacitor for developing a charge, first variable resistance means for adjusting the rate of charge of said first capacitor and first circuit means coupled to said first capacitor and said gating means and responsive to a first predetermined charge level on said first capacitor for switching said gating means from said first to said second condition.
 3. The invention as set forth in claim 2 wherein said second charging means includes a second capacitor for developing a charge, second variable resistance means for adjusting the rate of charge of said second capacitor and second circuit means coupled to said second capacitor and said gating means and responsive to a second predetermined charge level on said second capacitor for switching said gating means from said second to said first condition.
 4. The invention as set forth in claim 3 wherein said gating means comprises an SCR having cathode and anode electrodes respectively connected in series with the potential source and the device, and a gate electrode coupled to the first circuit means, and wherein in said first condition said SCR is nonconductive and in said second condition said SCR conducts.
 5. The invention as set forth in claim 4 wherein said first and second circuit means each respectively include a unijunction transistor. 